A norbornene-based polymer which is obtained by polymerization of a polymerizable monomer which contains a norbornene-based monomer in the presence of a metathesis polymerization catalyst is excellent in electrical characteristics, mechanical characteristics, impact resistance, heat resistance, weather resistance, etc., so is being increasingly used in a broad range of fields of shaped articles.
Such a norbornene-based polymer is, for example, produced by the reaction injection molding method of charging a reaction solution which includes a polymerizable monomer which includes a norbornene-based monomer and a metathesis polymerization catalyst in a mold and causing bulk polymerization.
However, a norbornene-based monomer is high in reactivity with respect to a metathesis polymerization catalyst, so the inconvenience ends up arising that if mixing these in advance, a polymerization reaction ends up proceeding and a good shaped article cannot be obtained. Accordingly, to prevent such an inconvenience from arising, when using the reaction injection molding method etc. to obtain a norbornene-based polymer, the monomer solution which contains the norbornene-based monomer and the catalyst solution which contains the metathesis polymerization catalyst have had to be separately prepared and the separately prepared monomer solution and catalyst solution have had to be made to instantaneously mix by an collisional mixing device etc. right before being charged into the shaping mold.
Further, in such a reaction injection molding method, since the method of mixing the monomer solution and catalyst solution right before charging them into the shaping mold is employed, when producing a relatively large shaped article, a good shaped article is obtained, but when trying to obtain a small shaped article (for example, a shaped article with a weight of less than 100 g), if using the monomer solution and the catalyst solution in large amounts in order to increase the mixing ability of the monomer solution and the catalyst solution, the material loss becomes excessive, while with small amounts, the mixability becomes insufficient and resultant parts with insufficient curing end up locally present and a good shaped article cannot be obtained.
On the other hand, Patent Document 1 discloses a polymerization method which improves the polymerization stability by adding a retardant etc. when polymerizing a mixture which contains a norbornene-based monomer and metathesis polymerization catalyst so as to set the gel time of the mixture at 15 seconds or more. Here, the gel time in Patent Document 1 means the so-called “gelation time” from when the metathesis polymerization catalyst is added to the monomer solution which contains the norbornene-based monomer to when the norbornene-based monomer reacts and gelates due to the action of the metathesis polymerization catalyst.